Some more typechecking bugs

[dibyendumajumdar]

function x(a: integer, b: integer[])
        local a1 = a[0]
end

It should not be possible to index an variable that is marked as integer. This will fail at runtime except if someone sets a meta-table on integer.

But following should fail:

function x(a: integer)
        local a1:integer = a[0]
end